Timer¶
Because ACRN is a flexible, lightweight reference hypervisor, we provide limited timer management services:
- Only lapic tsc-deadline timer is supported as the clock source.
- A timer can only be added on the logical CPU for a process or thread. Timer scheduling or timer migrating are not supported.
How it works¶
When the system boots, we check that the hardware supports lapic tsc-deadline timer by checking CPUID.01H:ECX.TSC_Deadline[bit 24]. If support is missing, we output an error message and panic the hypervisor. If supported, we register the timer interrupt callback that raises a timer softirq on each logical CPU and set the lapic timer mode to tsc-deadline timer mode by writing the local APIC LVT register.
Data Structures and APIs¶
Interfaces Design¶
-
static void
initialize_timer(struct hv_timer *timer, timer_handle_t func, void *priv_data, uint64_t fire_tsc, int32_t mode, uint64_t period_in_cycle)¶ Initialize a timer structure.
- Remark
- Don’t initialize a timer twice if it has been added to the timer list after calling add_timer. If you want to, delete the timer from the list first.
- Return
- None
- Parameters
timer: Pointer to timer.func: irq callback if time reached.priv_data: func private data.fire_tsc: tsc deadline to interrupt.mode: timer mode.period_in_cycle: period of the periodic timer in unit of TSC cycles.
-
static bool
timer_expired(const struct hv_timer *timer)¶ Check a timer whether expired.
- Parameters
timer: Pointer to timer.
- Return Value
true: if the timer is expired, false otherwise.
-
int32_t
add_timer(struct hv_timer *timer)¶ Add a timer.
- Remark
- Don’t call it in the timer callback function or interrupt content.
- Parameters
timer: Pointer to timer.
- Return Value
0: on success-EINVAL: timer has an invalid value
-
void
del_timer(struct hv_timer *timer)¶ Delete a timer.
- Return
- None
- Remark
- Don’t call it in the timer callback function or interrupt content.
- Parameters
timer: Pointer to timer.
-
void
timer_init(void)¶ Initialize timer.
- Return
- None
-
void
calibrate_tsc(void)¶ Calibrate tsc.
- Return
- None
-
uint64_t
us_to_ticks(uint32_t us)¶ convert us to ticks.
- Return
- ticks
-
uint64_t
ticks_to_us(uint64_t ticks)¶ convert ticks to us.
- Return
- microsecond
-
uint64_t
ticks_to_ms(uint64_t ticks)¶ convert ticks to ms.
- Return
- millisecond
-
uint64_t
rdtsc(void)¶ read tsc.
- Return
- tsc value
-
uint32_t
get_tsc_khz(void)¶ Get tsc.
- Return
- tsc(KHz)